Carbon stocks in major soil types and land-use systems in semiarid tropical region of southern India

The present study was conducted to study the soil organic and inorganic carbon stocks under different land-use systems in Warangal district, Andhra Pradesh, representing semiarid tropical region of India. Results indicated that Vertisols and associated soils contained greater total C stocks, followed by Inceptisols and Alfisols. The soil organic carbon (SOC) stock was highest in Alfisols (52.84 Mg ha(-1)) followed by Inceptisols (51.26 Mg ha(-1)) and Vertisols and associated soils (49.33 Mg ha(-1)), whereas soil inorganic carbon (SIC) stock was highest in Vertisols and associated soil (22.9 Mg ha(-1)) followed by Inceptisols (17.5 Mg ha(-1)) and Alfisols (12.4 Mg ha(-1)). Among the different land-use systems, total C stock was highest in forest soils followed by fodder system, paddy, maize, cotton, redgram, intercrop, chilli, permanent fallow and lowest in castor system. Soil nitrogen also followed similar trend as SOC stock. Significant correlation (P < 0.05) was obtained between SOC stock and soil nitrogen with Mandal-wise annual rainfall. A surface map of soil C stock and soil N was prepared for Warangal district using kriging interpolation techniques and total C stock was estimated to 0.088 Pg out of which SOC stock was 77% and SIC stock was 23% for the district. A relationship was established between Walkey-Black Carbon and SOC estimated through dry combustion method using CN analyser and it was found that Walkley-Black carbon could recover 90% of SOC for semiarid tropical soils.